Self-supporting tyre for vehicle wheels and method for manufacturing the same

Abstract

A self-supporting tyre ( 1 ) has reinforcing structures at the beads ( 4 ) defining rest surfaces ( 4 a ) for a corresponding rim ( 1 a ) which have a profile converging towards the tyre rotation axis away from the equatorial plane (X-X) of the tyre itself. The carcass plies ( 3 a, 3 b ) are each made by sequential deposition of strip-like sections circumferentially distributed on a toroidal support ( 11 ). Elastic-support inserts ( 16, 21 ) are interposed between the side portions ( 13 a, 14 a ) of axially internal sections ( 13 ), axial intermediate sections ( 15 ). In this manner around at least one of said support inserts opening degree of which can be modulated depending on requirements, by modifying the land/empty space ratio determined by the distance existing between the side portions ( 13 a, 14 a, 15 a ) of the strip-like sections ( 13, 14, 15 ) covering each of the axially opposite sides of the support insert itself.

1. A self-supporting tyre for vehicle wheels, comprising:
 a carcass structure having at least one carcass ply provided with end flaps in engagement with respective annular reinforcing structures disposed in coaxial relationship with a rotation axis of the tyre at positions axially spaced apart from each other and each incorporated into a tyre bead, at least one of said beads exhibiting, at a radially internal position thereof, a rest surface that, in a diametrical section plane of the tyre, defines a profile converging towards the rotation axis of the tyre and away from an equatorial plane of the tyre; 
 a belt structure applied to the carcass structure at a radially external position thereof; 
 a tread band applied to the belt structure at a radially external position thereof; 
 at least one pair of sidewalls each extending between one of said beads and a side edge of the tread band, at a position axially external to the carcass structure; 
 at least one pair of elastic-support inserts incorporated into the carcass structure, each at one of said sidewalls; 
 wherein the elastic-support inserts have respective radially internal apices placed close to the beads, and radially external apices close to side edges of the tread band, 
 wherein said at least one carcass ply comprises axially internal strip-like sections and axially external strip-like sections, 
 wherein the axially internal and axially external strip-like sections are circumferentially distributed around said rotation axis and each extends in a “U”-shaped configuration around the cross-section profile of the carcass structure, to define: two side portions mutually spaced apart in an axial direction, and a crown portion extending at a radially external position between the side portions, 
 wherein said elastic-support inserts are each axially interposed between side portions of the axially internal sections and side portions of the axially external sections. 
 
   
   
     2. A tyre as claimed in  claim 1 , further comprising:
 axially intermediate strip-like sections circumferentially distributed around said rotation axis and each extending in a “U”-shaped configuration around the cross-section profile of the carcass structure to define two side portions overlapping, at an axially external position, 
 wherein the elastic-support inserts comprise: 
 a crown portion extending in a radially external position between the side portions, and 
 a pair of auxiliary elastic-support inserts each axially interposed between the side portions of the axially intermediate sections and the side portions of the axially external sections. 
 
   
   
     3. A tyre as claimed in  claim 2 , wherein:
 the axially internal sections are distributed according to a circumferential pitch corresponding to a multiple of their width; 
 the axially intermediate sections are distributed according to a circumferential pitch corresponding to a multiple of their width and each have the respective crown portion interposed in circumferential approaching relationship between the crown portion of two axially internal sections, to define a first carcass ply therewith; and 
 the axially external sections are distributed according to a circumferential pitch substantially corresponding to their width, to define a second carcass ply radially superposed on the first carcass ply close to said crown portions. 
 
   
   
     4. A tyre as claimed in  claim 2 , further comprising:
 a second axially intermediate strip-like sections circumferentially distributed around said rotation axis and each extending in a “U”-shaped configuration around the cross-section profile of the carcass structure to define two side portions partly overlapping, at an axially external position, the side portions of the first axially intermediate sections; and 
 a crown portion extending in a radially external position between the respective side portions. 
 
   
   
     5. A tyre as claimed in  claim 2 , wherein:
 the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a multiple of their width; 
 the first axially intermediate sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, with the respective crown portion interposed in circumferential approaching relationship between the crown portions of two axially internal sections, to define a first carcass ply therewith; 
 a second axially intermediate sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; and 
 the axially external sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, with the respective crown portion interposed in circumferential approaching relationship between the crown portions of two of said second axially intermediate sections, to define a second carcass ply therewith, which second carcass ply is radially superposed on the first carcass ply close to said crown portions. 
 
   
   
     6. A tyre as claimed in  claim 2 , wherein:
 the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a width of each of the first axially intermediate sections, to define a first carcass ply; 
 the axially intermediate sections are distributed according to a circumferential pitch corresponding to a multiple of a width of each of the first axially intermediate sections; and 
 the axially external sections are distributed according to a circumferential pitch corresponding to a multiple of a width of each of the first axially intermediate sections and each have the respective crown portion interposed in a circumferential approaching relationship between the crown portions of two axially intermediate sections, to define a second carcass ply therewith, said second carcass ply is radially superposed on the first carcass ply close to said crown portions. 
 
   
   
     7. A tyre as claimed in  claim 2 , wherein the axially internal, intermediate and external sections respectively, are distributed according to a circumferential distribution pitch which is a multiple of a width of each of the first axially intermediate sections, in accordance with a numerical factor corresponding to the number of series of inner, intermediate and outer sections provided in forming said at least one carcass ply. 
   
   
     8. A tyre as claimed in  claim 7 , wherein the crown portions of the individual inner, intermediate and outer sections are sequentially interposed in a mutual approaching relationship along a circumferential line, whereas the respective side portions are axially offset from each other to house at least one of said elastic-support inserts in empty spaces or gaps existing between the side portions of the inner and intermediate sections and between the side portions of the intermediate and outer sections. 
   
   
     9. A tyre as claimed in  claim 2 , wherein:
 the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; 
 the axially intermediate sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections and each have the respective crown portion disposed circumferentially close to the crown portion of an axially internal section; and 
 the axially external sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each with its crown portion in circumferential approaching relationship between the crown portion of one of the axially internal sections and the crown portion of one of the axially intermediate sections, to define said at least one carcass ply therewith. 
 
   
   
     10. A tyre as claimed in  claim 1 , wherein the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, the axially external sections each having the respective crown portion interposed in circumferential approaching relationship between the crown portions of two axially internal sections. 
   
   
     11. A tyre as claimed in  claim 1 , wherein the axially internal sections and axially external sections are distributed according to a circumferential pitch corresponding to the width of each section, to define a first carcass ply and a second carcass ply respectively, the second carcass ply being radially superposed on the first carcass ply close to said crown portions. 
   
   
     12. A tyre as claimed in  claim 1 , further comprising a pair of auxiliary elastic-support inserts each disposed at an axially internal position with respect to the axially internal sections. 
   
   
     13. A tyre as claimed in  claim 1 , wherein each of said strip-like sections substantially extends in a plane parallelly offset from a meridian plane of the tyre, so that the respective crown portion, with respect to a radial reference plane passing through the transition point between the crown portion itself and at least one of the corresponding side portions, is oriented so that the crown portion forms an angle of a value different from the inclination of the side portions. 
   
   
     14. A tyre as claimed in  claim 13 , wherein the axially internal sections and axially external sections lie in deposition planes that at respectively opposite sides are offset from said meridian plane, so that at least the side portions of the axially internal sections have a crossed orientation relative to the side portions of the axially external sections. 
   
   
     15. A tyre as claimed in  claim 1 , wherein at least one of said annular reinforcing structures comprises:
 at least one stiffening element applied against said at least one carcass ply and having a cross-section profile extending away from the rotation axis of the tyre; and 
 at least one annular circumferentially-inextensible anchoring insert having a cross-section profile of flattened conformation, extending axially away from the stiffening element in a direction converging towards the geometric rotation axis of the tyre, away from the equatorial plane thereof. 
 
   
   
     16. A tyre as claimed in  claim 15 , wherein the cross-section profile of the annular reinforcing structure has a geometric centre of gravity located at such a position that an axially external end edge of said annular anchoring insert is pushed towards the rotation axis of the tyre following a tension generated along said at least one carcass ply by effect of an inflation pressure of the tyre. 
   
   
     17. A tyre as claimed in  claim 15 , wherein the cross-section profile of the annular reinforcing structure has a geometric centre of gravity located at an axially external position with respect to said stiffening element and at an axially internal position with respect to an axially external end edge of said annular anchoring insert. 
   
   
     18. A tyre as claimed in  claim 15 , wherein said stiffening element is axially positioned between a respective axially internal end flap and a respective axially external end flap of said at least one carcass ply. 
   
   
     19. A tyre as claimed in  claim 15 , wherein said annular anchoring insert is applied against an end portion of an outer end flap of the carcass ply, said end portion extending axially away from the equatorial plane of the tyre. 
   
   
     20. A tyre as claimed in  claim 19 , wherein said annular anchoring insert is applied at a radially external position with respect to said end portion of the outer end flap. 
   
   
     21. A tyre as claimed in  claim 15 , wherein said annular anchoring insert is disposed substantially close to a radially internal edge of the stiffening element. 
   
   
     22. A tyre as claimed in  claim 18 , further comprising at least one auxiliary annular anchoring insert parallel to and radially close to said annular anchoring insert. 
   
   
     23. A tyre as claimed in  claim 22 , wherein said auxiliary anchoring insert is applied at a radially external position with respect to an end portion of said inner end flap, extending axially away from an equatorial plane of the tyre. 
   
   
     24. A tyre as claimed in  claim 23 , wherein said auxiliary anchoring insert is applied at a radially internal position relative to said end portion of the outer end flap. 
   
   
     25. A tyre as claimed in  claim 15 , further comprising at least one auxiliary circumferentially-inextensible stiffening element having a cross-section profile radially extending at an axially internal position relative to said stiffening element. 
   
   
     26. A method of manufacturing a self-supporting tyre for vehicle wheels, comprising the steps of:
 preparing a carcass structure having at least one carcass ply provided with end flaps in engagement with respective annular reinforcing structures disposed in coaxial relationship with a rotation axis of the tyre at positions axially spaced apart from each other and each incorporated into a tyre bead, wherein the at least one of said beads exhibiting, at a radially internal position thereof, a rest surface that, in a diametrical section plane of the tyre, defines a profile converging towards the rotation axis of the tyre and away from an equatorial plane of the tyre; 
 wherein preparation of the carcass structure comprises: 
 arranging strip-like sections, each comprising longitudinal and parallel thread-like elements; 
 laying down axially internal strip-like sections circumferentially distributed on the toroidal support, each of said axially internal strip-like sections extending in a “U”-shaped configuration around the cross-section profile of the toroidal support, to define two side portions that are mutually spaced apart in an axial direction, and a crown portion extending in a radially external position between the side portions; 
 applying at least one pair of elastic-support inserts at an axially external position to the side portions of the axially internal sections, each at one of said sidewalls, wherein the elastic-support inserts have respective radially internal apices placed close to the beads, and radially external apices placed close to side edges of the tread band; 
 laying down axially external strip-like sections circumferentially distributed on the toroidal support, each of said axially external sections extending in a “U”-shaped configuration around the cross-section profile of the toroidal support, to define two side portions mutually spaced apart in an axial direction, each extending in an axially external position relative to one of the elastic-support inserts, and a crown portion extending in a radially external position between the side portions; 
 applying a belt structure to the carcass structure at a radially external position thereof; 
 applying a tread band to the belt structure at a radially external position thereof; and 
 applying a pair of sidewalls to the carcass structure, at laterally opposite positions of the latter, each of said sidewalls extending between one of said beads and a side edge of the tread band. 
 
   
   
     27. A method as claimed in  claim 26 , wherein before deposition of the axially external sections the following further steps are carried out:
 laying down axially intermediate strip-like sections circumferentially distributed around said rotation axis and each extending in a “U”-shaped configuration around the cross-section profile of the carcass structure to define two side portions overlapping, in an axially external position, said elastic-support inserts, and a crown portion extending in a radially external position between the side portions; and 
 applying a pair of auxiliary elastic-support inserts, at an axially external position, to the side portions of the axially intermediate sections, before deposition of the axially external sections. 
 
   
   
     28. A method as claimed in  claim 27 , wherein:
 the axially internal sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; 
 the axially intermediate sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, with the respective crown portion interposed in a circumferential approaching relationship between the crown portions of two axially internal sections, to define a first carcass ply therewith; and 
 the axially external sections are laid down according to a circumferential distribution pitch substantially corresponding to a width of each of the first axially intermediate sections, to define a second carcass ply therewith, said carcass ply being radially superposed on the first carcass ply. 
 
   
   
     29. A method as claimed in  claim 28 , wherein before application of said auxiliary elastic support insert, and wherein the axially intermediate strip-like sections are first axially intermediate strip-like sections, the method comprising:
 laying down second axially-intermediate strip-like sections circumferentially distributed around said rotation axis and each extending in a “U”-shaped configuration around the cross-section profile of carcass structure to define two side portions partly overlapping, at an axially external position, the side portions of the first axially intermediate sections being previously laid down, and a crown portion extending in a radially external position between the respective side portions. 
 
   
   
     30. A method as claimed in  claim 29 , wherein:
 the axially internal sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; 
 the first axially intermediate sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each having the respective crown portion interposed in a circumferential approaching relationship between the crown portions of two axially internal sections, to define a first carcass ply therewith; 
 the second axially intermediate sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; and 
 the axially external sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each having the respective crown portion interposed in a circumferential approaching relationship between the crown portions of two of said second axially intermediate sections, to define a second carcass ply therewith. 
 
   
   
     31. A method as claimed in  claim 27 , wherein:
 the axially internal sections are laid down according to a circumferential distribution pitch substantially corresponding to a width of each of the first axially intermediate sections, to define a first carcass ply; 
 the axially intermediate sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; and 
 the axially external sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each having the respective crown portion interposed in a circumferential approaching relationship between the crown portions of two of said intermediate sections, to define a second carcass ply therewith, which carcass ply is radially superposed on the first carcass ply close to said crown portions. 
 
   
   
     32. A method as claimed in  claim 27 , wherein:
 the axially internal sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections; 
 the axially intermediate sections are laid down according to a circumferential distribution pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each having the respective crown portion disposed circumferentially close to the crown portion of an axially internal section; and 
 the axially external sections are laid down according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, each having its crown portion in circumferential approaching relationship between the crown portion of one of the axially internal sections and the crown portion of one of the axially intermediate sections, to define said at least one carcass ply therewith. 
 
   
   
     33. A method as claimed in  claim 26 , wherein the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a multiple of a width of each of the first axially intermediate sections, the axially external sections being each laid down with the crown portion in circumferential approaching relationship between the crown portions of two axially internal sections. 
   
   
     34. A method as claimed in  claim 26 , wherein the axially internal sections are distributed according to a circumferential pitch substantially corresponding to a width of each of the first axially intermediate sections to define a first carcass ply, and the axially external sections are distributed according to a circumferential pitch substantially corresponding to a width of each of the first axially intermediate sections to define a second carcass ply radially superposed on the first carcass ply close to said crown portions. 
   
   
     35. A method as claimed in  claim 26 , further comprising the step of arranging a pair of auxiliary elastic-support inserts, each at an axially internal position with respect to the axially internal sections. 
   
   
     36. A method as claimed in  claim 26 , wherein each of said strip-like sections is laid down in a plane parallelly offset from a meridian plane of the toroidal support. 
   
   
     37. A method as claimed in  claim 36 , wherein the axially internal sections and axially external sections are respectively laid down in deposition planes that are offset at respectively opposite sides from said meridian plane, so that the side portions of the axially internal and axially external sections have respectively inclined orientations. 
   
   
     38. A method as claimed in  claim 26 , wherein accomplishment of at least one of said annular anchoring structures comprises the steps of:
 applying at least one annular circumferentially-inextensible anchoring insert in radial superposed relationship with an end portion of at least one of said end flaps, said anchoring insert having a cross-section profile of flattened conformation extending axially away from the corresponding inner end flap and from an equatorial plane of the tyre; and 
 applying at least one stiffening element against said at least one end flap, said stiffening element being substantially placed at an axially internal position relative to said annular anchoring insert and having a cross-section profile extending away from said rotation axis. 
 
   
   
     39. A method as claimed in  claim 38 , wherein application of said annular anchoring insert takes place by winding at least one thread-like element in concentric coils disposed axially close to each other around the toroidal support. 
   
   
     40. A method as claimed in  claim 38 , wherein application of said annular anchoring insert is carried out subsequently to deposition of the axially external sections. 
   
   
     41. A method as claimed in  claim 38 , wherein application of the stiffening element is carried out before application of the annular anchoring insert. 
   
   
     42. A method as claimed in  claim 38 , wherein application of said at least one stiffening element is carried out before deposition of the axially external sections. 
   
   
     43. A method as claimed in  claim 38 , wherein application of said at least one stiffening element is carried out by winding at least one thread-like element in concentric coils that are radially superposed around the toroidal support. 
   
   
     44. A method as claimed in  claim 38 , further comprising the step of applying an auxiliary circumferentially-inextensible annular anchoring insert disposed substantially parallel and radially close to said annular anchoring insert. 
   
   
     45. A method as claimed in  claim 38 , wherein an auxiliary anchoring insert is applied subsequently to deposition of the radially internal sections and before deposition of the radially external sections. 
   
   
     46. A method as claimed in  claim 45 , wherein application of said auxiliary anchoring insert takes place by winding up of at least one thread-like element in concentric coils disposed axially close to each other around the toroidal support. 
   
   
     47. A method as claimed in  claim 38 , wherein before applying said stiffening element, application of at least one auxiliary stiffening element radially extending in an axially internal position relative to the stiffening element is carried out. 
   
   
     48. A method as claimed in  claim 47 , wherein application of said auxiliary stiffening element preferably takes place by winding at least one thread-like element in concentric coils disposed radially close to each other around the toroidal support. 
   
   
     49. A method as claimed in  claim 26 , wherein each of said elastic-support inserts is formed by winding at least one continuous strip-like element of elastomer material so as to form coils that are disposed axially close to and/or radially superposed on each other around the geometric axis of the toroidal support.